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Legacy A/C conversion - R12 to R134a

Well I just finished up the conversion on my 1990 Legacy today to R134a. I must say, the conversion wasn't that hard and the results are good. I know people bitch and moan that converting doesn't work and blah blah blah. If you do it right, it works fine.

I'm goin to give a little tutorial on the basics of what needs to be done to have a successful swap.

The first thing that needs to be done is the system discharged. You can do this the "proper" way by using a vacuum pump, or just loosen one of the bolts a little and let things vent......<em>you shouldn't do this....but I can't stop you</em>

Next you need to get all the old oil out of the system. Most of it will be in the compressor and receiver/dryer. You will need to replace the receiver/dryer anyway, so you can leave that alone right now.

Unfortunately to get the oil out of the A/C compressor, you will need to take it out. Loosen the belts for the alternator & a/c, remove the lines from the compressor, and unbolt the compressor. Once you get it out, dump out the oil from the intake & discharge holes. Turn the compressor clutch a couple times to get any excess oil out. There is also a drain hole on the side of the compressor. It wouldn't be a bad idea to remove that and make sure everything's completely out.

Leave the compressor out for the time being.

Next remove the lines that connect to the receiver dryer, and also remove the pressure sensor. Once you have them disconnected, loosen the bolt that holds the clamp down on the receiver/dryer.

Check all the o-rings and make sure they're good. If they're good, you don't need to replace them. Mine were fine.

Next take some compressed air and blow through the line that goes to the condensor from the compressor. Put a rag under that line at the receiver/dryer to catch any oil or other gunk that comes out.

If you get any nasty black goo, or anything that looks bad, you should probably flush the system with some flush stuff.

At this point, you have the option to take the evaporator box out. You don't need to take it out, however gunk, leaves, etc gather in there and can cause things to stink up pretty bad. Mine was nasty.

Needless to say I took my evap box out. It really wasn't that difficult. You must first remove the lines that connect to the lines in the evap box. Once you do that you will need to take out the glove box, and the plate that it bolts to. There is a bolt at the bottom and nut at the top of the evap box. Remove those two and the whole thing comes right out.

I cleaned everything up with pinesol. It worked very well.

Once you get it clean, put it back in, in reverse order.

Now you're ready to put everything back together.

As I mentioned, you will need a new receiver/dryer. Just get the one for your car at a local autoparts store. I got mine at autozone for 45 bucks.

I guess now is as good as any to talk about other supplies.

Oil. r134a & r12 refrigerants use different oils. The oil acts as a means of transportation for the refrigerant. R12 systems use mineral oil. Most newer 134a systems use PAG oil. PAG oil is a synthetic oil. It however has zero compatibility with mineral oil. So it's not the best choice when doing a conversion.

Esther oil however does work with r134a, and is compatible with mineral oil. So you don't have to get every last drop of mineral oil out. However you should try to get as much as you can out.

So, while you're at the parts store, you will need a receiver/dryer, some esther oil, and some r134a refrigerant.

Note, you probably don't want to get the refrigerant that has oil and other crap in it. As it will probably have incompatible oil in it.

Now let's talk about the amount of oil & r134a you will need.

It will vary for different vehicles, but on mine, it said to put in about 5 oz. of oil. When you put the oil in, you want to put about 1 oz in the receiver dryer, and then put the rest in the suction port on the compressor.

For refrigerant. You want to fill the system to about 75-80% of the original r12 capacity. Mine called for about 1.8-2.0 lbs of R12, so I used 1.5 lbs of R134a.

Last thing you will need is the new R134a fittings.

So....now that you have all your supplies....time to put everything back together.

Like I mentioned, put about 1 oz of the esther oil in the receiver/dryer, and put the lines and the pressure sensor in it. The receiver/dryer should come with new o-rings....you can put those on.

Pour the remaining esther oil that your system calls for in the compressor, like mentioned above. Now the compressor is ready to bolt back in the car. Bolt it back in and connect the high and low pressure side lines. Put all your belts and such back together.

Now put on the new fittings, and you should be ready to pull a vacuum. I took my car to a shop at this point, since I couldn't find a place to rent a vacuum pump and it cost more to buy one then to just take it to a shop.

The hooked the vacuum pump up, sucked all the air out. This also boils all the water out of the system. Once it was all out. They let it sit for 10 min to make sure there was no leaks. He added as much refrigerant as he could with the car off, and then had me start it, and finished adding the appropriate amount of 134a.

That's it. It really wasn't that hard, and she blows nice and cold air. Only issue I have is that since I have an underdrive pulley on, the compressor really isn't spinning fast enough at idle speed. If I get ambitious I may swap it out for a non-underdriven, but lightened pulley. We'll see.

I got a deal on labor for the vacuum and charge....that may be a little more, depending on the shop you go to.

Not bad for $120.00, and it won't cost an arm and leg to recharge.

Also, forgot to mention I had the aid of a buddy who told me most of what I just told you. Plus he recommended the Haynes Heating & Air conditioning tech book. I think it was like $15. It has all the oil amounts & refrige amounts too.

Very helpful, and would highly recommend you get one if you are planning on do a/c work yourself

10425 - Automotive Heating & Air Conditioning, Covers theory and operation of all heating and air conditioning systems in use today. Step-by-step procedures are provided for diagnosis, maintenance and repair.

Got to ask, why convert if system working fine? If system has lost pressure it means there is a leak and that should be fixed. I am told there will be oil at the point of leakage. It may not be an issue for Subarus but my understanding is that R134a needs higher pressure to obtain same cooling as R12 so the compressor is likely to wear faster as it cycles more often.R12 is selling for $20 on eBay with a 609 certificate. Certificate may be obtained by taking an online test for $20. Another board for helpful A/C information is www.aircondition.com.

The system wasn't working fine, that's the reason I swapped it. Plus, recharge, service, maintenance in the future will only get more expensive.

The previous compressor was knocking, and after taking everything apart, it was pretty obvious why.....there was little to no oil in the system. Plus I wanted to take the evap box out and clean it out.

I agree with you, if it ain't broke, no need to fix it. However mine was definitely not working properly, and in Houston having a/c is a necessity.

I am 100% satisfied with the results.

I've put a pretty decent amount of research into this. What I've done is IMO a cost effective method/option to convert your system over and still maintain good performance. I've looked at what the OEM retrofits consist of, talked to several dealers, as well as run everything by a buddy who did a/c tech work. I basically mirrored his setup. He did his swap about two years ago when his compressor went out. His still blows cold to this day. He thinks there's a small leak, but he can't find it. So just add a little bit a refrige every 2-3 years. Not a big deal in my mind.

I may have a similar leak.....but the cost of adding some refrige every two years is far less expensive then completely going over the entire system and replacing all the o-rings, etc, etc.

Wish I would've known about the online test and so forth before hand, thanks for the info.

It is reccomended that you aso replace the o-rings if you remove a line etc . They don't cost much & can sometimes be the fix for that pesky leak . If your car is 13 years old , I would have done that while in there . You can also add dye that will help find leak . You have to use a blacklight to see it . :cool:

The o-rings on the receiver/dryer were replaced. I didn't replace the other ones. There was no evidence of leaking in the other spots. I think there was some leaking in and around the evap box, but I'm not sure if that was just excess junk or oil from the a/c system.

If I had another car and more time....I probably would've took the time and pulled the expansion valve and everything off and found new o-rings......but I don't....and it sucks....

There was a little bit of dye in the manifold that the tech used to charge the system up.......so I do have some dye in there.

I liked the pictures and description Josh. It looks like there is a little oil on the expansion valve. Do you know how the leaves and debris get into the evaporator box? Would it be worthwhile placing mesh or a filter by the air intake or only using it in recycle mode?

The leaves and gunk get in there through the air inlet which is in the sill underneith the wiper area. leaves and other junk are bound to get in there. Some get stuck in the fan and cause noise.....I've already cleaned them out of there once before. Apparently some managed to get by the fan and into the evap box. I suppose you could put a screen somewhere, but then leaves would pile up there.......so it's a catch 22.....you'll have to clean the screen or the evap out at some point and time....so I guess just pick which one you want to do

Yeah it probably wouldn't have hurt to replace the o-rings on all that stuff, and/or possibly even let the evaporator box soak in some pinesol or something to help clean out the rest of the gunk in the fins. I did the best I could, but it's definitely not perfect.

On the first gen legacies the only mode that uses recirc is a/c max. All others draw outside air.

Large scale ozone losses have occurred above the Arctic this past winter with over 50% of the ozone destroyed at altitudes around 18 km. ...

Overall temperatures in the ozone layer were the lowest for 50 years .... large areas of polar stratospheric clouds (PSCs) - clouds in the ozone layer- were present over the Arctic region at altitudes between 14 and 26 km. This [area] is the largest in the 50 year record, and especially in the last 20 years, the period when the ozone-depleting compounds have been high.

The chemical balance in the stratosphere is changed significantly by the presence of these clouds, altering the breakdown products from manmade CFCs (chlorofluorocarbons) so that rapid chemical ozone destruction can occur in the presence of sunlight. The cold conditions affected the distribution of nitrogen oxides, allowing ozone loss to continue longer than usual.

..... the atmospheric concentrations of CFCs [has] started to decrease. But the atmospheric lifetime of these compounds is extremely long and the concentrations will remain at dangerously high levels for another half century.

... the Arctic ozone layer will mainly depend on ... temperatures at the altitude of the ozone layer. Over the past forty years the conditions there have become significantly colder.... the cold Arctic winters.... result in large ozone losses. In 2005 the average extent of conditions cold enough... was four times larger than it has ever been ....

This continuous cooling trend is ... a result of increasing concentrations of greenhouse gases in the atmosphere [and so will continue].

I think the only thing I would probably do different is use PAG oil instead of esther. I've had one compressor go out on me. I don't know if it was just coincidence.......and the compressor I have in now is knocking. I don't know if it's due to the fact esther oil doesn't lubricate as well as PAG oil, or the fact that the guy who pulled a vacuum on the system, didn't do it long enough.

I might just be having bad luck with used compressors. I've got my own set of gauges and vacuum pump, so I know it'll be done right the next time. I'm probably going to swap out the compressor when I do my motor swap some time this summer. That or when the current compressor craps out, I'll swap it out.

Don't re-use the old O rings, if you have the system apart, replace them with R-134a compatible O-rings, they are not that expensive, and if they've been on there a while they have probably flattened out anyway, so the $5 or so it'd run ya for a set of O rings is worth it. Also, the PAG oil is not compatible wiht mineral oil, however the mineral oil will coat the inside of the refirgerant lines, which will help keep the R-134a in the system. I've never used Esther oil, I used PAG when I converted my Legacy over to R-134a. You can switch to an R-134a compressor if you have one, but it's not needed... You can get a "retrofit kit" that has refrigerant, fittings, and the thing to charge it for relatively cheap ($40-50) at most auto parts stores, but you need to remove ALL the R-12 and pull a vacuum on the system before you attempt to put it in, because if you mix the two it's considered hazardous waste, and you'd have to pay $400 or so to have it disposed of :-) Also stay away from the bootleg/black market R-12, especially the stuff from Mexico, since most of it is a mixture of R-12, R-22, and Butane (which is FLAMMABLE) and are not approved by the EPA so are not only considered hazardous waste, are also illegal to sell or use in the US... (Although I have heard of people charging A/C systems with propane, which apparently works better than R-12, you better not have a leak :-P) I'd also recommend against using compressed air to blow out the lines, just flush them with the proper flush agent (There is some stuff they make for flushing transmission coolers that comes in a spray can, I wonder if that would work???) as compressed air contains oil and moisture and other crap you don't want in your A/C system. Black goo ususally means the compressor has gone south, sending aluminum filings through the system (Called "Black Death" by most techs) which requires flushing the entire system, as those filings will destroy the new compressor!